Ask the Coaches: Dizziness and Heart Rate

Jan 1, 2001

Q: My daughter is an accomplished Cross-Country runner, having placed at State her sophomore year. As her junior year wears on, she finds herself hitting a wall 2/3 of the way, getting light headed, and nearly collapsing in the last race. We are in a small town, in a rural area and the docs are not experienced with athletes. Her blood tested fine, but when they did a treadmill test, they thought her heart was beating too fast (190 on a max rate of 205). The doc has ordered an echocardiagram at a larger hospital tomorrow (wed) but her district meet is Thursday. The doc has prescribed beta blockers to keep her heart from beating so fast, but after reading some of your responses- I am not sure it is wrong to run 85-90% of max rate. Could this be a glycogen deficiency or something of that nature? It was only in the 50's for the last meet but she did have a very fast start. Could you comment on racing heart rate and whether dizziness (and leg fatigue) is necessarily related to that.

A: Maximum heart rate according to the formula 220-age can be very inaccurate. It is possible that your daughter's hear rate may reach higher than 220 beats/minute.

Dizziness during exercise is cause for concern and needs to be evaluated. The echocardiogram will evaluate for heart problems which may cause dizziness; it will check the thickness of the heart muscle and the function of the valves. This is an important test.

Other causes of dizziness include exercise induced asthma and dehydration; she may not drink enough on a regular basis and start the race dehydrated.I think that you have made an important observation - she starts her races fast. By doing so, she is developing lactic acid if she is exceeding the level where her body can take in enough oxygen to meet the demands. This may make her hyperventilate, which can cause dizziness and tingling/numbness. The build up of lactic acid can make a runner feel terrible.

Most athletes do not tolerate beta blockers, because they prevent the heart rate from increasing in response to exercise. This will probably have a negative impact on running fast.

If your daughter had symptoms on the treadmill, while her heart rate was high, then she may require medications; if she was not symptomatic, then the test probably reflects her normal response to exercise.

A Part of Hearst Digital Media
Runner's World participates in various affiliate marketing programs, which means we may get paid commissions on editorially chosen products purchased through our links to retailer sites.